Spinning quench chamber having a conical flow director

ABSTRACT

A CYLINDRICAL CHIMMEY USED FOR QUENCHING SYNTHETIC FILAMENTS AFTER THEY ARE EXTRUDED FROM A SPINNERET IS DIVIDED INTO CONCENTRIC CYLINDRICAL PLENUM AND QUENCHING CHAMBERS BY MEANS OF A CYLINDRICAL FORMATIONS MEMBER COMPRISED OF AT LEAST FIVE LAYERS OF FINE MESH SCREENS SPACED FROM EACH OTHER A SPECIFIED DISTANCE TO IMPROVE QUENCH MEDIUM DISTRIBUTION FROM THE PLENUM INTO THE QUENCH CHAMBER. A CONE SHAPED FLOW DIRECTOR EXTENDS FROM THE SPINNERET COAXIALLY INTO THE QUENCHING CHAM-   BER. A FLOW RESTRICTOR AT THE EXIT END OF THE QUENCH CHAMBER FORMS A PARTIAL SEAL WITH THE FILAMENT BUNDLE DIRECTING THE AIR FLOW THROUGH THE BUNDLE FOR MORE EFFICIENT COOLING. A GUIDE POSITIONED BELOW THE CHIMNEY QUENCH CHAMBER ENCOMPASSING THE FILAMENTS SERVES TO STABILIZE THE THREADLINE AND IS VERTICALLY MOABLE TO VARY THE FILAMENT BUNDLE SIZE AT THE POINT IT PASSES THROUGH THE FLOW RESTRICTOR TO VARY THE SEALING EFFECT OF THE BUNDLE.

June 27, 1972 CALDWELL ETAL 3,672,801

SPINNING QUENCH CHAMBER HAVING A CONICAL FLOW DIRECTOR Filed Jan. 13, 1971 04 4 OODOE INVENTORS GARY LEE CALDWELL RICHARD THOMAS EGER FREDERICK WARREN MILLER United States Patent Ofice 3,672,801 Patented June 27, 1972 3,672,801 SPINNING QUENCH CHAMBER HAVING A CONICAL FLOW DIRECTOR Gary Lee Caldwell, Wilmington, Del., and Richard Thomas Eger, Madison, and Frederick Warren Miller, Hendersonville, Tenn., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del.

Filed Jan. 13, 1971, Ser. No. 106,022

Int. Cl. Dllld 13/02 US. Cl. 425-71 4 Claims ABSTRACT OF THE DISCLOSURE A cylindrical chimney used for quenching synthetic filaments after they are extnuded from a spinneret is divided into concentric cylindrical plenum and quenching chambers by means of a cylindrical foraminous member comprised of at least five layers of fine mesh screens spaced from each other a specified distance to improve quench medium distribution from the plenum into the quench chamber. A cone shaped flow director extends from the spinneret coaxially into the quenching chamber. -A flow restrictor at the exit end of the quench chamber forms a partial seal with the filament bundle directing the air flow through the bundle for more efiicient cooling. A guide positioned below the chimney quench chamber encompassing the filaments serves to stabilize the threadline and is vertically movable to vary the filament bundle size at the point it passes through the flow restrictor to vary the sealing effect of the bundle.

BACKGROUND OF THE INVENTION The invention relates to the melt spinning of synthetic, organic polymers to form filaments. More particularly, it relates to an improved quenching apparatus for use in melt spinning operations.

An important step in the production of synthetic, organic filaments by melt spinning is the provision of a quenching device to cool and solidify the streams of molten polymer emerging from the spinning orifices.

Various methods of quenching have been proposed, each having apparatus designed to provide a uniform flow of air in the vicinity of the filaments. For example, one method uses a cross-flow quenching apparatus in which the molten streams of polymer are cooled and solidified by passing a stream of air across their path. Another method uses a quenching apparatus in which air is directed radially inwardly against the molten filaments and thereafter flows cocurrently with the filaments as they travel downward.

While these types of apparatus are generally satisfactory for the commercial production of synthetic filaments, there is a need for a quenching apparatus which can provide increased quenching capability for spinning productivity increases without accompanying losses in filament uniformity and spinning continuity. The present invention fulfills that need.

SUMMARY OF THE INVENTION The quenching apparatus of this invention includes a spinneret from which filaments are extruded as a circularshaped hollow bundle and a cylindrical elongated chimney positioned below the spinneret through which the filament bundle passes for quenching by a gas supplied to the chimney. A cylindrical foraminous member concentric with the chimney which divides the chimney into a quenching chamber and a plenum chamber is comprised of at least 5 layers of fine meshed screen spaced from each other, a distance of from about 0.03 inch to 0.05 inch. A cone shaped flow director extends coaxially from the spinneret into the quenching chamber and serves to direct gas flowing through the filament bundle downwardly out the chimney. The exit of the chimney is partially restricted by a reduced opening closure plate closely surrounding the filament bundle as it passes out from the chimney to form a partial seal at this opening, thus, forcing the air in the quenching chamber to penetrate through the bundle for more efiicient cooling. The sealing efiect may be regulated by placing a vertically movable guide below the closure plate opening. The guide has an opening through it approximating the shape of the closure plate opening. Movement of the guide up or down can regulate the proximity of the filaments in the outer periphery of the bundle to the edge of the closure opening.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a sectioned elevation of a preferred embodiment of the apparatus of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In its preferred embodiment, the apparatus of this invention is used in the melt spinning of high molecular weight isotactic polypropylene. However, it may also be used in the production of filaments from other melt spinnable polymers such as polyesters and polyamides.

The apparatus illustrated includes a spinneret plate 2, connected to a pressured source of molten polymer 1 and an exhaust device 3 positioned between the spinneret plate and a radial chimney or quench device 4. Extending downwardly into the radial chimney 4 from a cylindrical spacer 16 attached to spinneret 2 is a conical flow director 5. The flow director is coaxial with and extends almost to the bottom of chimney 4. A plate 8 having a central opening 9 therethrough is attached to the exit of chimney 4. Positioned below chimney 4 is a movable guide 7 having an opening 10 that is in coaxial alignment with opening 9. The smoke removal device 3 and chimney 4 are sealed against one another and against the spinneret to form a substantially airtight chamber around the filaments 6 as they pass from spinneret 2 through the chimney.

Chimney 4 is comprised of a cylindrical jacket 20 which in conjunction with a concentric cylindrical screen member 18 divides the chimney into a plenum chamber 21 and a quenching chamber 17. Screen member 18 is surrounded by a perforated cylindrical distribution element 22. An exit tube 19 extends downward from member 18. Foraminous screen member 18 is formed from at least five wraps of fine mesh screen spirally wound into a cylindrical form with a spacing of 0.03-0.05 inch between adjacent screens. In the preferred embodiment, ten cylinders of mesh screen are used, the spacing between adjacent cylinders being provided by two layers of coarser 18 mesh screen. The use of spaced screens provides more uniform air flow than the same number of screens without spacing. -A surprising feature of this invention is the degree of air flow uniformity improvement achievable with such small spacings between screens making it possible to obtain highly uniform flow fields with relatively thin packs.

Plenum chamber 21 is supplied with air or other cooling gas at a pressure slightly above atmospheric, through inlet 23 in jacket 20 to a distributing chamber 25 around the exit tube 19 and thence through annular orifice 24 to plenum chamber 21.

Guide 7 can be moved up and down to control the size of the filament bundle and its position relative to closure plate 8. The opening 10 in the guide controls the shape of the bundle which is generally either round or oval. The shape of opening 9 in plate 8 conforms to that of opening 10. Movement of guide 7 can be used to vary the degree of sealing of the threadline at opening 9 thus providing a measure of control in the amount of air penetrating the bundle. In addition, guide 7 serves to stabilize the threadline.

A smoke removal device has been found necessary in the melt spinning of polypropylene containing certain stabilizing additives which tend to sublime at the spinning temperatures forming fumes at the spinneret face. Smoke removal device 3, which is not an essential feature of this invention, can be used to eliminate such fumes where this is a problem. The device consists of a truncated, hollow, inverted cone-section 11, communicating via a series of small orifices 12 with annular chamber 13, formed between concentric generally cylindrical members 14 and 15. Suction is applied to chamber 13 and provides the means for removing the smoke. Where smoke is not -a problem, the smoke removal apparatus can be eliminated and the radial quench positioned immediately below the spinneret 2.

The invention is further illustrated by the following examples.

Example I Polypropylene having a Melt Flow Rate 1 (MFR) of 2.8 was melt spun at 270 C. from a spinneret having 500 orifices arranged in five concentric circles of 100 orifices each, using an apparatus similar to that shown in the drawing. The foraminous member 18 was composed of five layers of 100 mesh screen (30.3% open area) each layer separated by two layers of 18 mesh screen (70.2% open area) to provide a spacing of about 0.036 inch between the 100 mesh screens. The perforated cylinder 22 had 0.054 inch diameter holes uniformly, spaced to provide an open area of 3.75%. The inverted cone was 17 inches long with a 4 inch diameter base mounted to the spinneret through a 2 inch long insulating cylindrical spacer. A 4% x 5 /8 inch oval-shaped flow restrictor was used at the quench exit but no threadline stabilizing guide was used.

At a throughput of 1.36 g./min./hole, using a quench flow rate of 330 c.f.m. and a smoke removal rate of 90 c.f.m., stringup of the threadline was successful and the filaments were passed over a set of feed and draw rolls at a draw ratio of 3.0x. Spinning continuity was acceptable with only two breaks occurring in 75 minutes.

Example II The experiment of Example I was repeated except that the inverted cone and exit flow restrictor were removed and the spaced screens were replaced by five layers of 100 mesh screen tightly wound upon each other. The filament line could not be collected due to excessive dripping.

Example III A wind tunnel study was conducted to examine the flow field resulting from the passage of air through a perforated plate and screen arrangement similar to that of the quench unit of Example H. High velocity jets, created by air flow passage through the restricting holes in the perforated plate, were found to penetrate the screen and to be distinguishable in the flow field for a distance of at least 1 inch downstream from the screen. Since the outside row of fibers in Example II cam within /5 inch of the screen, such jets evidently come in contact with the threadline causing it to be jostled, the end result being dripping of the threadline. At a distance of V2 inch from the screen and at an equivalent quench flow of 314 c.f.m., this study showed a jet peak velocity of 8.8 ft./sec. and a null or valley velocity minimum between adjacent jets of 2.8 ft./sec. Based on the jet peak, this represents a 68% variation in velocity within a transverse distanct of /8 inch.

ASTM-D 1238-62-1 at 230 C. and 11. load of 2,160 gins.

Additional tests conducted under the same conditions but with a spaced screen arrangement equivalent to that of Example I showed that, at /2 inch from the screens, the jet peak velocity had been reduced to 4.0 ft./sec. with a concomitant increase in minimum valley velocity to 3.7 ft./sec. Thus, the velocity variation was reduced almost an order of magnitude to 7%. Of particular im portance here is that the jets were reduced to this minimal level by a device that could be incorporated within the space limitation in the quench apparatus.

A similar arrangement, but having ten layers of mesh screen spaced by the double layers of 18 mesh screen, was also tested. Little or no further reduction in velocity variation due to jetting was noted.

Example IV The spinning test of Example I was repeated using the same apparatus except that foraminous member 18 was replaced by one having ten layers of 100 mesh screen each separated by two layers of 18 mesh screen and that a threadline stabilizing guide (1% inch x 5 inch oval) was mounted 26 inches below the quench exit. This arrangement provided further improvements in spinning continuity, at the same spinning conditions, with only one break occurring in 1,030 minutes of operation. Good operability was also obtained when the exit flow restrictor was replaced by a circular one having a 5 inch diameter opening and the threadline stabilizing guide was replaced by a round one having an internal diameter of 3 inches.

Although no improvement in jetting reduction was seen with the ten layer versus the five layer spaced screen, measurements did show an overall improvement in quench air flow uniformity. The spinning test of Example I was repeated with all essential apparatus details remaining generally the same except that a ten layer spaced screen was used in place of the five layer spaced screen. Spinning continuity was observed to improve over that of Example I, thus indicating the benefificial effect of the improved overall quench air flow uniformity. It might be further noted that the overall quench air flow uniformities measured on the spaced screens were better than that measured on the standard screen of Example 11. Therefore, the improved spinning continuity of Example I over Example II can be attributed not only to a reduction in jetting but also to an improvement in overall quench air flow uniformity.

What is claimed is:

1. In an apparatus for the production of synthetic filaments including a spinneret, a cylindrical elongated chimney positioned below the spinneret and means connected to the chimney for supplying a quenching medium thereto, the improvement comprising: a cylindrical foraminous member concentric with said chimney dividing said chimney into a quenching chamber through which filaments pass as a hollow bundle from said spinneret and a plenum chamber, said foraminous member comprising at least five layers of fine mesh screen spaced from each other a distance of from about 0.03 inch to 0.05 inch; a cone shaped flow director extending from said spinneret coaxially into said chamber substantially the entire length of said chamber; and a means surrounding said bundle for restricting the flow of quenching tioned below said chimney, said guide having an opening of substantially the same shape as the opening through the flow restricting means and being movable toward and away from said flow restricting means to regulate filament proximity to said restricting means.

References Cited UNITED STATES PATENTS 3,067,458 12/1962 Dauchert 188 QD UX 3,070,839 1/1963 Thompson 188 QD UX 3,080,607 3/1963 Bley 18-8 QD UX 6 3,280,542 10/1966 Heijnis 55485 3,299,469 1/1967 Charlton 18-8 QM FOREIGN PATENTS 1,410,427 9/1969 Germany 18--8 QM J. SPENCER OVERHOLSER, Primary Examiner M. O. SUTTON, Assistant Examiner US. Cl. X.R. 425464 

